Conventionally, programmable controllers (hereinafter, “PLCs”) are used for controlling production facilities. Engineering apparatuses are connected to such PLCs to perform predetermined programming processes or maintenance. Generally speaking, an engineering apparatus operates in a personal computer and has a function of supporting creation of a computer program used for the control exercised by the PLCs as well as connecting the personal computer in which the engineering apparatus is operating to the PLCs, transferring the created computer program to the PLCs, and monitoring the state in which the PLCs are exercising control.
Each of the PLCs has a base (a “back plane”) so that a communication unit used for a network connection is attached to the base. By connecting two or more communication units to one another via a communication line such as a cable, a control system that includes a plurality of PLCs is constructed. In a control system for a large-scale production facility, a large number of PLCs are used. In that situation, the networks that connect the PLCs to one another also have complicated configurations.
Some of the engineering apparatuses described above are capable of creating network configurations of the control system offline, displaying the network configurations with graphics, and monitoring the PLCs and transferring computer programs to the PLCs by using the graphic display. In some situations, however, a control system having a complicated configuration includes a plurality of PLCs of mutually the same type, and it is difficult to distinguish the PLCs that require settings from the other PLCs, on a screen displayed by the engineering apparatus. To cope with this situation, a technique for displaying, with highlight, PLCs that are the targets in a monitoring process or a setting process has been proposed (see, for example, Patent Document 1).    Patent Document 1: Japanese Patent Application Laid-open No. 2006-277734